This invention relates to test equipment for ultrasonic diagnostic imaging systems and, in particular, to Doppler flow phantoms for measuring and testing colorflow and Doppler sensitivity.
Phantoms are devices which are in widespread use to evaluate and calibrate to performance of ultrasound systems. A phantom is a box-like device containing tissue-mimicking material. Tissue-mimicking materials are substances which have an acoustic response which is closely matched to that of the human body. Generally such a material is strongly water based such as a gelatinous material, into which is mixed particles or other materials which simulate the acoustic scattering effect of the body. Phantoms usually contain objects of know size and dimensions at various depths in the phantom. These objects, such as small balls, fluid-filled balloons and pockets of fluids, provide specular an other characteristic targets which are sharply imaged when the ultrasound system is properly focused, or simulate pathology such as cysts and tumors that test the ability of the ultrasound system to detect or visualize such targets.
A particular type of phantom which is used to test and evaluate Doppler ultrasound capabilities is the flow phantom. A flow phantom generally consists of tissue-mimicking material with tubing passing therethrough. A liquid is pumped through the tubing to simulate a vessel with blood flowing through it. A Doppler probe is pressed into contact with the top surface of the tissue-mimicking material which simulates the skin surface, and an effort is made to image the flowing liquid or measure its velocity. In this way the flow phantom enables the Doppler capabilities of an ultrasound system to be evaluated and measured.
When Doppler ultrasound first came into use it was predominately used to measure flow in shallow (superficial) vessels such as the carotid artery, as the capability was ineffective or unreliable at deeper depths in the body. But as Doppler ultrasound system performance and sensitivity have improved over the years it has become possible to perform Doppler imaging and make Doppler measurements at ever-increasing depths in the body. Consequently there is now a need for phantoms to provide the ability to test the performance of Doppler imaging and measurement at greater depths. But a phantom simulating a greater depth must necessarily be larger and bulkier than previous phantoms. This is undesirable, as phantoms should be highly portable so they can be easily transported to the sites of different ultrasound systems where they are used. There exists a need for an ultrasound phantom to be compact, yet still enable the evaluation of ultrasound system performance at substantial imaging and measurement depths.
In accordance with the principles of the present invention, a flow phantom is provided having multiple fluid paths, each of which is designed to provide Doppler performance evaluation at a different range of depths or angle of incidence. The combination of the multiple paths provides the ability to measure Doppler sensitivity and performance over a significant range of depths without requiring a significantly larger phantom than those currently in use.